Commercial motor vehicles, particularly large diesel powered semi trucks, are taxed relatively heavily for their operation on public roads. Annual registration and licensing fees are considerably more than those typically charged to the owners and operators of privately owned passenger cars and vehicles, but fuel taxes are the major means of tax revenue from such large trucks.
At the time of preparation of the present disclosure, diesel fuel for highway use was Federally taxed at a rate of 24.4 cents per gallon, with additional state taxes averaging around another 20 cents per gallon, depending upon the state where the fuel was sold. Thus, Federal and state taxes alone account for approximately one third or more of the cost of such diesel fuel. Yet, not all such fuel is burned on public roads and highways. Trucks commonly spend a large percentage of their time while parked with their engines running at idle, due to the relative difficulty in starting large diesel engines, particularly when cold; studies have found that trucks may average eight hours per day parked with the engine idling.
It is generally more economical in the long run to allow such an engine to run at idle, where it is burning on the order of one gallon of fuel per hour, than to shut it down and restart it later, which results in wear and tear on the starter system, cold start abrasion of particularly the upper cylinder walls due to lack of lubrication at startup, and other adverse factors. Indeed, in extremely cold conditions, it is common to allow such engines to run continuously to provide heat to the fuel, which can increase in viscosity to the point of becoming a gel in extremely cold conditions, and also to the trucks cab.
However, such idling while parked will typically cost the operator of the truck on the order of 40 to 45 cents per hour just in terms of fuel taxes, at the typical fuel burn of one gallon per hour at idle. While it is legally required that motor vehicle operators pay taxes on fuels used in transportation on public roads, thereby providing for their construction, maintenance, and repair, there is no legal requirement for such taxes to be paid on fuels which are not used on public roads. Thus, the typical truck could see savings of over three dollars per day in typical use, just by burning untaxed fuel while parked with the engine at idle.
Accordingly, a need will be seen for an apparatus or system which provides for the automatic switching of the fuel system from a fuel tank containing taxed fuel, to an auxiliary fuel tank containing untaxed fuel, while the motor vehicle is parked. The system must be fully automatic in operation and beyond control of the operator, to ensure that the less expensive untaxed fuel will always be used where legally permissible, and further to ensure that only taxed fuel will be burned in over the road use while traveling on public roads, streets, and highways.